The proposed studies will be performed in cats and human subjects. They will investigate: 1) The neuromuscular properties of the sphincter of Oddi; 2) The sphincter of Oddi interaction with chemical messengers (neuropeptides and endogenous chemicals); 3) Physiological interactions between the sphincter of Oddi and the gallbladder or duodenum; and, 4) Pharmacological and clinical applications of measurements of sphincter of Oddi pressures. The electrical and mechanical activity of the sphincter of Oddi will be studied in vivo and the length-force relationships of the sphincter of Oddi strips will be studied in vitro in cats. The electrical activity will be recorded using bipolar electrodes. The sphincter of Oddi pressures will be recorded by a constant perfused open-tipped probe which will measure resistance to flow and by a probe with the side-opening which will measure circular muscle squeeze. Gallbladder pressures will be measured after the gallbladder is filled with a physiological volume of saline or during a constant filling to determine pressure-volume curves. The LES pressures will also be measured simultaneously to examine the similarities and differences between the sphincter of Oddi and the LES. The human sphincter of Oddi will be evaluated with a manometric probe introduced through the duodenoscope. These studies will be conducted in control subjects and in patients believed to have functional disorders of the sphincter of Oddi. The neuromuscular characteristics of the SO and the mechanisms of action of the chemical messengers (neuropeptides and endogenous chemicals) will be studied with a pharmacological analysis.